1. Field of the Invention
The present invention relates to a color-based sorting apparatus in which it is determined whether grains to be sorted, such as cereal grains are defective or not based on the color of each grain while the grains are being transferred along a predetermined transference path, and when a grain is determined to be inferior, the inferior grain is sorted out.
2. Description of the Related Art
It is necessary to sort cereal grains such as rice grains or soybean into non-defective grains which can be commercialized and defective grains which cannot be commercialized in a predetermined refining process after harvesting. Particularly, in a case of polished rice, unless foreign substances or rice grains discolored in black, brown or the like are previously removed as defective grains as far as possible, the commercial value thereof may be deteriorated. Further, in many other cereal grains than polished rice as well, if foreign substances or defective grains discolored due to spoilage and/or damage or the like are mixed in, the commercial value of the grains may be deteriorated.
Accordingly, a color-based sorting apparatus has been conventionally proposed in which cereal grains such as rice grains or soybeans are sorted and separated based on reflection factors thereof. In this type of color-based sorting apparatus, there is a color-based sorting apparatus provided with a supplying section for supplying cereal grains to a sorting section, an image pickup section for picking up images of cereal grains under a predetermined quantity of light, a determination section for determining each grain whether the grain is defective or not based on the obtained image, and a sorting section for sorting out the grains which are determined as defective grains.
In the aforementioned color-based sorting apparatus, cereal grains slide and move in a predetermined groove of a narrow flowing passage (a so-called chute) which is sloped and is provided in the supplying section, and fall down from a terminal portion of the supplying section through a predetermined path. Images of each of the grains which are falling are picked up by the image pickup section which includes a photoelectric sensor or the like at an inspection position in a midstream of a falling path, and the density of the obtained image and a predetermined threshold value relevant to density are compared with each other. Based on this comparison result, each grain is determined whether it is defective or not. Further, the grain determined as a defective grain is sorted out by being discharged from the predetermined falling path by blowing air from a high-pressure air valve.
Since the aforementioned conventional color-based sorting apparatus is structured to convey cereal grains to slide through the narrow flowing passage (chute) to send the cereal grains to the inspection position, the speed at which the grains slide through the flowing passage varies depending on properties (moisture or the like) of each grain. Further, cereal grains may frequently fall through the flowing passage jumping and rolling down depending on the shapes of the grains (particularly, soybeans). As a result, the locus of the grains falling through the flowing passage or the speed at which the grains fall becomes irregular. Hence, a timing to sort out each grain in the sorting section after a camera picks up an image in the image pickup section may be off, or a grain may miss the sorting region. Therefore, it is difficult to carry out sorting of defective grains of cereal grains such as rice grains or soybeans with high accuracy.
In order to solve the aforementioned problem, a color-based sorting apparatus using a belt conveyor has already been proposed by the assignee of the present application (see Japanese Patent Application Laid-Open (JP-A) No. 9-122606). In the color-based sorting apparatus disclosed therein, cereal grains on a belt conveyor neither slide, roll nor jump, and fall from the belt conveyor in a stable state. For this reason, the falling-locus of the grains and the speed at which the grains fall becomes regular and defective grains of cereal grains such as rice grains or soybeans can be sorted out with high accuracy.
However, in the aforementioned color-based sorting apparatus using a belt conveyor, practically uses a belt conveyer including a large number of components, and therefore, production costs increase. Further, when a belt conveyor is used, an operation of periodically adjusting tension of a belt or an operation of adjusting twisting of a belt needs to be carried out, thereby resulting in complicated maintenance.